Abstract: A cask has an inner rectangular enclosure of stainless steel fitting, with a slight clearance in the similarly shaped interior of a generally rectangular body of depleted uranium serving as a gamma ray shield. A cylindrical shell surrounds the generally rectangular gamma ray shield and copper partitions divide the annular space therebetween into a plurality of compartments for a neutron absorbing liquid. Flow paths between compartments are provided without removing copper from the partitions or interrupting any radial heat conduction path of any partition. Transverse partitions in certain of the compartments provide for holding the radial thickness of the liquid generally uniform throughout the circumference of the cask.